There are more than 5 exchanges with over 1000XBT volume.
BitStamp
BitFinex
Okcoin
Btc-e
LakeBtc
BtcChina
Huobi
Kraken
And some others as well, but their volume is generated mostly by Altcoins, for that reason I didn't mention them.
Hard to compare the volume when some exchanges are charging 0 fee.